1. Field of the Invention:
The present invention, in general, relates to four wheel drive transfer case shift levers and, more particularly, to devices that convert a single lever transfer case shifter into a dual lever arrangement for internal-linkage types of transfer cases.
Factory equipped four wheel drive types of vehicles generally have a transfer case that is used to shift from either two-wheel drive mode (normal) to four-wheel drive mode (slippery roads). The transfer case also selects between a high and a low range of gears.
Usually, a single lever is supplied by the factory that is used to accomplish the gear changes from two-wheel drive into four-wheel drive and once in four-wheel drive from high gear range into low gear range.
For some people this arrangement is satisfactory even though it includes certain limitations. For others it is not.
For example, many drivers who regard their off-road vehicular use as a sport find a single lever to be too limiting. They would prefer to be able to select between two or four-wheel drive mode with one lever and then select the gear range with another lever.
While there are conversions that allow a driver to put a single lever shifter into a two-wheel drive low gear range, these positions have disadvantages and are discussed in greater detail hereinafter. It is important, however, to explain why a driver would want to put the transfer case into a two-wheel drive low gear range.
This position is useful when a driver is, for example, backing a boat trailer down a paved ramp into the water. A low gear range would allow the driver to xe2x80x9ccreepxe2x80x9d backwards making course corrections at a safe and comfortable low rate of speed. However, if the driver were forced to go into four-wheel drive in order to achieve the low gear range, then as he made the steering corrections, binding of the gears would occur on the pavement. Clearly, this is not desirable.
Transfer cases come in two varieties that include external linkages and internal linkages. Conversion xe2x80x9ckitsxe2x80x9d are known that can change an external linkage single lever transfer case into a dual lever transfer case for use with four-wheel drive vehicles.
This is fairly easy to achieve as the linkages are exposed outside of the transfer case. Therefore, it is possible to adapt a separate lever to readily engage with each of the linkages.
However, those vehicles that have an internal linkage four-wheel drive transfer case heretofore have been impossible to convert from a single lever into a dual lever arrangement. This is because there has been no way to access into the transfer case and then to separate the functions in such a way that would permit the use of two levers.
These types of internal linkage transfer cases are found on certain types of common imported vehicles, for example, with TOYOTA brand four wheel drive vehicles.
Presently, there is no known way to convert an internal- linkage 4WD transfer case from single lever to dual lever usage. That does not mean that it is impossible to get an internal transfer case having a single shift lever into two-wheel drive low gear range.
There are two basic ways to achieve getting an internal linkage transfer case into two-wheel drive low range. The first is by removal of a center detent ball from the transfer case. If this is accomplished, it may be possible to use the single shift lever to access two-wheel drive low gear, however it results in a complicated shift pattern and is therefore not desirable.
A second way includes the removal of the center detent ball and elongation of a shift arm slot in the shift fork shaft. When this type of a conversion is accomplished and the shift lever is in either the two-wheel drive low gear range or in the four-wheel drive high gear range, the shift lever is free to xe2x80x9cflopxe2x80x9d out of place. When this happens, even though the transfer case stays in the correct range and drive mode, the shift lever is prone to jamming when the driver attempts to shift into another setting.
Therefore, current modifications made to an internal-linkage transfer case so as to enable the use of a single shift lever to access a two-wheel drive low gear range have provided unsatisfactory results.
Accordingly there exists today a need for a device to convert an internal-linkage 4WD transfer case from single lever to dual lever use.
Clearly, such an apparatus would be a useful and desirable device.
2. Description of Prior Art:
Mechanisms and devices appertaining to transmissions and transfer cases are, in general, known. For example, the following patents describe various types of these devices:
U.S. Pat. No. 2,173,044 to Ruggles et al., Sep. 12, 1939;
U.S. Pat. No. 2,290,089 to Bock, Jul. 14, 1942;
U.S. Pat. No. 2,329,916 to Lamb et al., Sep. 21, 1943;
U.S. Pat. No. 4,281,735 to Sloma, Aug. 4, 1981;
U.S. Pat. No. 4,325,450 to Ward, Apr. 20, 1982;
U.S. Pat. No. 4,332,304 to Barnow, Jun. 1, 1982;
U.S. Pat. No. 4,646,584 to Okbo et al., Mar. 3, 1987;
U.S. Pat. No. 4,719,814 to Ida et al., Jan. 19, 1988;
U.S. Pat. No. 4,989,473 to McMorris, Feb. 5, 1991;
U.S. Pat. No. 5,954,612 to Baxter, Jr., Sep. 21, 1999; and
U.S. Pat. No. 6,000,296 to Sundquist, Dec. 14, 1999.
While the structural arrangements of the above described devices, at first appearance, have similarities with the present invention, they differ in material respects. These differences, which will be described in more detail hereinafter, are essential for the effective use of the invention and which admit of the advantages that are not available with the prior devices.
It is an object of the present invention to provide a two-lever shift mechanism for an internal-linkage transfer case that can adapt a single-lever internal-linkage transfer case for use with dual-levers.
It is also an important object of the invention to provide a two-lever shift mechanism for an internal-linkage transfer case that allows a four wheel drive vehicle having an internal-linkage transfer case to access a low gear range while it is in the two-wheel drive mode.
Another object of the invention is to provide a two-lever shift mechanism for an internal-linkage transfer case that can be modified to fit a variety of four-wheel drive vehicles that have an internal-linkage type of a transfer case.
Still another object of the invention is to provide a two-lever shift mechanism for an internal-linkage transfer case that has a positive xe2x80x9cfeelxe2x80x9d and is reliable to use.
Still yet another object of the invention is to provide a two-lever shift mechanism for an internal-linkage transfer case that is easy to install.
Yet another important object of the invention is to provide a two-lever shift mechanism for an internal-linkage transfer case that includes a seal (i.e., a boot) to protect the interior of the transfer case from the elements, such as rain, mud, and snow.
Still yet another important object of the invention is to provide a two-lever shift mechanism for an internal-linkage transfer case that is inexpensive to manufacture.
Briefly, a two-lever shift mechanism for an internal-linkage transfer case apparatus for use with four-wheel drive vehicles that have an internal-linkage type of a transfer case which is constructed in accordance with the principles of the present invention has a sleeve that is adapted to fit into a housing. The housing is attached to the transfer case and it includes an opening providing access into the transfer case. The sleeve includes a pivot pin passing through opposing walls that define a pivot axis. A first and a second arm are disposed in the sleeve and are adapted to pivot about the axis. A first shift lever and a second shift lever are each attached to the first and second arms respectively at one end thereof. At an opposite end thereof the first and second shift levers extend into the interior portions of the vehicle so that an operator can control (i.e., shift) them independent of each other. The first shift lever selects two-wheel or four-wheel drive mode operation. The second shift lever selects the high or low gear range. A protective rubber boot fits over both the first and second shift arms and at least a portion of the housing.